The Research And Application Of The Overload Control In The Mobile Softswitch System

With the development of mobile communication industry, developing the mobile softswitch network is the inevitable request of the business innovation and network evolution for the operators. In recent years, as the core equipment of communications network, softswitch is used in large-scale business. Customer's number that accommodated by it has became bigger and bigger. And it also provides various business categories. But instability of softswitch has been increased. However, customer's requirement about the stability of communications equipment and the quality of communication has been improved. Traffic of softswitch is faced with some extreme challenges. The existing overload control mechanisms no longer meet the requirements of current mobile networks. So we need to improve internal control software to make sure it is able to maintain good performance under high load conditions. So we can enhance the capability of the equipment itself and the entire network. The project makes sense of stability of the communication network.This paper is based on the experience of the author participating in the development of mobile softswitch system. Through the analysis about softswitch's circulating instance, such as the Mid-Autumn Festival, the Spring Festival and other traditional festivals, the original overload control system is not ascendant enough. Some interfaces don't agree with the protocol. There are some deficiencies in testing in connection with the other suppliers. In order to improve the stability and the compatibility of softswitch system, we need to develop a new overload control system of softswitch. The author took part in the service overload control parts of the project and his work is the design and development.As a key component in the core network, softswitch system connects the entities which come from the other side truck such as ISUP, TUP and BICC, and the access side such as BSC, RNC, and the network database such asHLR, SCP. There are three possible scenes when softswitch interacts with these entities. First, the business output of the mobile softswtich to the other side, leading the other side can not deal normally. After the other side sending a message to softswitch, in order to assist the other side recovering, softswitch needs to adjust its business to deal with the output. Second, the business input of the other side leads the mobile softswitch can not deal with business normally. Under this circumstances, softswitch need to discard certain business forcibly, or send a message to the other side to reduce business to keep itself recover. Third, the softswitch is normal, however, because the buffer is too small, the transmitting quality of the bottom becomes bad, or other reason, the protocol layers will lead the business transmitting channel overload.According to the analysis of softswitch system, the designs of the softswtich overload control can be divided into three parts: the overload control of the other side entity, the business overload control of the local, the overload control of the signal channel.Through the analysis of the other side entities such as BSC, RNC, SCP, MSC, HLR etc. the overload control according as the 3GPP and ITU, designed the requirements of overload control. The requirements contain four aspects as follows: BSC informs softswitch by OVERLOAD message that it is in the overload state, at the same time, it also demands softswitch to reduce business; RNC informed softswitch by OVERLOAD message that it is in the overload state, it also demands softswitch to reduce business; MSC informed softswitch with ACC that it is in the overload state, it also demands softswitch to reduce business; SCP informed softswitch by sending Call Gap that it is in the overload state, it also demands softswitch to reduce business.The business overload control in the business access points of the"business integrity"(for example, a call to the first piece of news, The first request for a business or any other piece of news) , refused or take the queue shaping the business in order to help the local out of the overload state. The business overload control uses the center control model. Access to theinterface of business users priority access to the data are mapped into a leaky bucket priority without the buffer devices The device needs to accept this judgment by the business priority, and the high priority the first. The priority leaky bucket with out a buffer is the combination of two buckets, including flood peak leaky bucket and priority confined ratio leaky bucket. Leaky bucket flood peak business including single and multi-service flood peak for the business rapidly discarded. In time to prevent a large flow of the access unit to avoid conducting system more effective and meticulous control before the collapse. Priority confined ratio leaky bucket is a real priority ratio composed of sixteen leaky bucket, a leaky bucket for each class. Priority for priority access business judgment decides whether to allow access to the priority level of the business which depends on the system allowed access flow.The overload control of the signal channel generally behaves buffer of the bottom lower becoming overload for some reason. Under such circumstances, the bottom signaling request the upper-users to reduce the business request by sending the state to users, and then it can become normal.The overload control system and the overload priority leaky bucket without the buffer device which presented by this paper mainly are applied in the overload control system of the mobile softswitch. Based on the system design, overload control system is divided into five parts: business management, signaling channel, overload control, monitoring overload, maintenance and management. The author participated in the development of business management and overload control. The product has released now, in the life time of the product has not recover the low capability case and paralysis. The stability of the device is high. In the busy time, it can also keep the high priority users first and attains a good evaluation of clients.